Tungsten oxytetrachloride,also known as Tungsten(VI) tetrachloride oxide, is an inorganic compound

Inorganic compound

Inorganic compounds have traditionally been considered to be of inanimate, non-biological origin. In contrast, organic compounds have an explicit biological origin. However, over the past century, the classification of inorganic vs organic compounds has become less important to scientists,...

 with the formula

Chemical formula

A chemical formula or molecular formula is a way of expressing information about the atoms that constitute a particular chemical compound....

 W

Tungsten

Tungsten , also known as wolfram , is a chemical element with the chemical symbol W and atomic number 74.A hard, rare metal under standard conditions when uncombined, tungsten is found naturally on Earth only in chemical compounds. It was identified as a new element in 1781, and first isolated as...

O

Oxide

An oxide is a chemical compound that contains at least one oxygen atom in its chemical formula. Metal oxides typically contain an anion of oxygen in the oxidation state of −2....

Cl₄

Chloride

The chloride ion is formed when the element chlorine, a halogen, picks up one electron to form an anion Cl−. The salts of hydrochloric acid HCl contain chloride ions and can also be called chlorides. The chloride ion, and its salts such as sodium chloride, are very soluble in water...

. This diamagnetic solid is used to prepare other complexes of tungsten. The orange-coloured compound is soluble in nonpolar solvents but it reacts with alcohols and water and forms adduct

Adduct

An adduct is a product of a direct addition of two or more distinct molecules, resulting in a single reaction product containing all atoms of all components. The resultant is considered a distinct molecular species...

s with Lewis bases.In aprotic acids this compound forms 1:1 adducts. The solid consists of weakly associated square pyramidal monomers.

WOCl₄ is prepared from tungsten trioxide

Tungsten trioxide

Tungsten oxide, also known as tungsten trioxide or tungstic anhydride, WO3, is a chemical compound containing oxygen and the transition metal tungsten. It is obtained as an intermediate in the recovery of tungsten from its minerals. Tungsten ores are treated with alkalis to produce WO3...

 with the following reaction: WO₃ + 2 SOCl₂

Thionyl chloride

Thionyl chloride is an inorganic compound with the formula SOCl2. It is a reactive chemical reagent used in chlorination reactions. It is a colorless, distillable liquid at room temperature and pressure that decomposes above 140 °C. Thionyl chloride is sometimes confused with sulfuryl...

  → WOCl₄ + 2 SO₂

Sulfur dioxide

Sulfur dioxide is the chemical compound with the formula . It is released by volcanoes and in various industrial processes. Since coal and petroleum often contain sulfur compounds, their combustion generates sulfur dioxide unless the sulfur compounds are removed before burning the fuel...

This compound can be stored for a few months, but needs to be stored in nitrogen at room temperature because tungsten(VI) oxytetrachloride is very moisture sensitive. The crystal structure of WOCl₄ is tetragonal. Tungsten(VI) tetrachloride oxide dissolves in aromatic and chlorinated solvents, but is insoluable in aliphatic hydrocarbons.

Reactions with Organic Acids

Tungsten (VI) oxytetrachloride [WOCl₄] reacts with organic acids performing a nucleophilic substitution by removing the chlorines. This reaction takes place by adding the organic acid with WOCl₄ and CS₂ and refluxing the solution in a water bath until all the HCl that is formed is evaporated off. The refluxing of HCl was confirmed because the product did not respond to a test for free chlorine, showing all the chlorine was substituted and boiled off. The compounds that are created with the select organic acids all produced a colored material, but some had different solubility results. In the case of the synthesis using lauric, mystic, palmitic and steric acids, the compounds formed were only slightly soluble in benzene. Further, all the compounds created were ruled stable in a dry atmosphere. The reactions prove that WOCl₄ will react with four monocarboxylic molecules or two molecules of dicarboxylic acids.

Reactions with Organic Compounds

Tungsten tetrachloride oxide reacts with organic compounds such as ketones, anilines, and amides. The samples were prepared by combining WOCl₄ in CS₂ and the organic compound in a flask; until the organic compound was added in excess. The solution was allowed to sit for 48 hours, and the precipitate was filtered and then washed with benzene to ensure that the entire organic compound was removed.

A general result for all compounds was the generation of a color that was different from the original orange red of tungsten tetrachloride, being stable in a dry atmosphere and the insolubility in benzene. Also, all compounds hydrolyzed when added to water and were decomposed by acids and alkalis. The numbers of molecules that are able to complex to the WOCl₄ varies based on the organic compound. Aminophenols can only combine two molecules with one molecule of WOCl₄ while ketones, amides, and anilides can combine four. The reason that ketones, amides and anilides have the ability to combine four molecules to one molecule of WOCl₄ is due to the carbonyl group and the strong affinity of tungsten towards oxygen.

Amino Derivatives

Tungsten (VI) oxytetrachloride creates amino derivates when reacted with secondary and tertiary amines. The compounds are created by adding a solution of the chosen amine in a benzene solution to WOCl₄ in CS₂ until the amine was in slight excess. The amines had different reactions while forming the compound; the secondary-amine compounds fell out of solution quickly while tertiary amines needed extra shaking time for the compound to form. These precipitates were filtered and washed with benzene until all of the starting amine reacted with the WOCl₄.

The compounds that were formed in the reaction between tungsten (VI) oxytetrachloride and amines are insoluble in benzene and ether, but partially soluble in ethanol, acetone and CS₂. The compounds that are created are stable in dry atmosphere, but if in a humid atmosphere will absorb water and decompose. A result of this experiment that seemed to show interesting promise is the reaction between dibenzylaniline and WOCl₄. Only two molecules of dibenzylaniline are able to bond with a single molecule of WOCl₄ which seems to be caused due to steric hindrance.

Catalytic Properties

There are a few catalysts that are created with WOCl₄ as the base of the catalyst. A few examples are listed:

Ternary catalyst: WOCl₄-n-Bu₄Sn-t-BuOH

Binary catalyst: WOCl₄-n-BuLi
WOCl₄-EtMgBr

These catalysts are used in assistance to induce the living polymerizations of the compound [o-(Trifluoromethyl)phenyl]acetylene.

Synthesis of the ternary catalyst:
The ternary catalyst (WOCl₄-n-Bu₄Sn-t-BuOH) is created by dissolving WOCl₄ into an anisole solution of n-Bu₄Sn, and the entire combined solution was then aged for 15 minutes. Another solution of anisole and t-BuOH was added to the WOCl₄-n-Bu₄-Sn solution. This final solution was allowed to again age for 15 minutes until the mixture turned a bluish-purple solution, and the reaction is complete.